Imaging in a scattering medium relates generally to the methods and techniques of generating an image of the internal properties of a scattering medium on the basis of detected scattered energy.
Many systems and techniques have been developed for imaging of scattering media. A typical system for imaging based on scattered energy detection includes a source for directing energy into a target medium and at least one detector, at one or more locations with respect to the source, for measuring the scattered energy exiting the target medium. From these measurements of energy exiting the target medium, it is possible to reconstruct images that represent the scattering and absorption properties of the target. The absorption and scattering properties of the medium are a function of the medium itself, and of the wavelength and type of energy employed as an imaging source.
Exemplary methods and systems for imaging of a scattering media are disclosed in Barbour et al., U.S. Pat. No. 5,137,355, entitled “Method of Imaging a Random Medium,” (hereinafter the “Barbour '355 patent”), Barbour, U.S. Pat. No. 6,081,322, entitled “NIR Clinical Opti-Scan System,” (hereinafter the “Barbour '322 patent”), U.S. Pat. No. 6,795,195, entitled “SYSTEM AND METHOD FOR TOMOGRAPHIC IMAGING OF DYNAMIC PROPERTIES OF A SCATTERING MEDIUM” by inventors R. L. Barbour and C. H. Schmitz (hereinafter the “Barbour '195 patent”), U.S. Pat. No. 6,937,884, entitled “METHOD AND SYSTEM FOR IMAGING THE DYNAMICS OF A SCATTERING MEDIUM” by inventor R. Barbour and is hereby incorporated by reference (hereinafter the “Barbour '884 patent”).
Imaging techniques based on these known systems and techniques measure the internal absorption and scattering properties of a medium using sources whose propagating energy is highly scattered. This permits the use of wavelengths and types of energy not suitable for projection imaging techniques. Thus these techniques have great potential for detecting properties of media that are not accessible to energy sources used for projection imaging techniques (e.g., x-rays).
As can readily be appreciated, there are many instances where these techniques are highly desirable. For example, one flourishing application is in the field of optical tomography. Optical tomography typically uses near infrared radiation (i.e., electromagnetic radiation with wavelengths in the range of ˜750–˜1200 nanometers) as an energy source. Near infrared radiation is highly scattered in human tissue and is therefore an unsuitable source for practical projection imaging in the human body. However, these properties make near infrared radiation a superior imaging source for scattering imaging techniques. The ability to use near infrared radiation as an imaging source is of particular interest in the human body because the strength of the interactions between the radiation and tissue are exceptionally responsive to blood oxygenation levels and blood volumes. These attributes permit imaging of the vasculature, and thus provide great potential for detecting cardiovascular disease, tumors and other disease states.
Of central importance to these and other imaging methods is an appreciation of the limits of sensitivity and achievable resolution of the reconstructed image. In the case of simple projection imaging, the properties of the point-spread function largely determine the sensitivity and resolution limits. In model-based techniques for imaging of scattering media, sensitivity and resolution are strongly influenced by a complex relationship between a host of parameters associated with the target properties (i.e., target domain), conditions and quality of collected data (i.e., measurement domain) and stability and accuracy of numerical methods used for image recovery (i.e., analysis domain). However, sensitivity and resolution are ultimately limited by the quality of the collected data. Known methods and systems for imaging of scattering media provide images having relatively low resolution and sensitivity.
For the foregoing reasons, there is an ongoing need for methods of improving the quality of the data collected from a scattering medium in a manner that enhances the resolution and sensitivity of the reconstructed image.